1. Field of the Invention
This invention relates to a novel, flexible, wettable, hydrophilic glass coated polysiloxane contact lens. The glass coated polymeric contact lens has properties in addition to being wettable and hydrophilic, such as, having a sufficient amount of oxygen transportability to meet the requirements of the human cornea, fillerless, flexible, hydrolytically stable, biologically inert, transparent, resilient and soft. The lens comprises an outer coating of substantially colorless transparent glass from about 100 to about 8000 angstroms thick. The glass may be silicate glasses, phosphate glasses, germanate glass or mixtures thereof. The substrate may be a polymer comprising a poly(organosiloxane) .alpha.,.omega. terminally bonded through a divalent hydrocarbon group to a polymerized activated unsaturated group.
2. Prior Art Statements
U.S. Pat. No. 2,674,743 teaches in pertinent part a contact lens made from a plastic material which contains a coating of silica on the surface of the lens. It is stated at column 2, lines 2-3 of '743 that the resinous materials are in the form of acrylic esters or polymers of styrenes or substituted styrenes. It is further stated at column 4 of '743 at lines 18-30 that plastic materials particularly resin plastics are preferred such as polymers of styrenes or substituted styrenes, although the esters of acrylic and methacrylic acids such as polymethyl methacrylate have been successfully used plus cellulosic plastics. However, no where does it disclose that silicone rubber material such as the polysiloxanes of the instant invention can be coated with glass material. All the substrate materials disclosed in '743 have glass transition temperatures above ambient temperatures i.e. room temperatures. The substrate material of the instant invention has glass transition temperatures below ambient temperatures i.e. room temperatures. Therefore, the plastic materials in '743 at room temperature are very hard materials as compared to a silicon rubber which, as mentioned, has a glass transition temperature below room temperature and is resilient and soft at room temperature. The instant invention comprises coating a rubbery material with glass whereas in '743 a hard plastic is being coated with silica.
U.S. Pat. No. 3,959,105 discloses in pertinent part an article composed of a silicon elastomer which includes silicon dioxide as a filler for the elastomer. The patent teaches that one may use plasma to oxidize and clean the surface of the silicon elastomer. As disclosed in '105 the elastomer uses a silicon dioxide filler and without the filler the silicon elastomer is not strong enough to be used for its intended purpose. In '105 after the ion bombardment the filler i.e., silicon dioxide, is exposed at these bombarded regions. The patent teaches that as a result, the surface of the article becomes hydrophilic. Also it is taught in '105 that the affects achieved are also due to the rupture of the silicon-oxygen and/or silicone-carbon bonds of the silicon elastomer during ion bombardment. It is taught in '105 that as a result of ion bombardment that the remaining regions of the outer silicon elastomer layer is transformed into activated silicon dioxide. In the instant invention there are no fillers involved in the polysiloxane substrate material. The instant material is using a fillerless siloxane material which is coated with glass. Also in the instant invention the applicant is coating a continuous layer of glass onto the siloxane material whereas in the teachings of '105 a continuous layer of silica is not being obtained on the surface. Only where the ions have bombarded away the elastomer is the silicon dioxide exposed. Applicant is not only exposing the surface of the instant material, i.e. substrate. to oxygen plasma in an RF field or exposing this substrate to sputter etching, but additionally the invention involves then coating the surface of the substrate with a continuous coating of glass. In the instant invention the applicant continues to coat glass on the surface of the substrate after the substrate has preferably already been oxidized. There is a significant difference between sputtering or coating silica on the surface of a fillerless siloxane material as in the instant invention and having the silica already in the silicone resin as a filler material and then bombarding the surface of the silicone resin with ions in order to expose the filler material wherever the bombardment is sufficient to remove the outer coating of the silicone resin.
U.S. Pat. No. 3,637,416 discloses, in pertinent part, the interposition of a thin continuous polymeric bonding film or layer composed of one or more silanes between the surface of a plastic or elastomeric material substrate and a deposit or coating of silica or silica gel. This final structure may be used to make contact lens. The formula which represents the compounds disclosed in '416 given at column 5, lines 16-23 are silanes and not siloxanes. These are not similar compounds to the siloxanes disclosed in the instant invention.
U.S. Pat. No. 3,708,225 discloses, in pertinent part, that contact lens may be made from polycarbonates and polystyrenes. However, the invention involves the interposition of a thin, continuous polymeric bonding film or layer composed of one or more silanes between the surface of a plastic or elastomeric material substrate and a deposit or coating of silica or silica gel. As mentioned above, silanes are much different compounds than the siloxane compounds used in the instant invention. The silanes disclosed at column 6 of '225 are completely different compounds than the siloxanes of the instant invention.
U.S. Pat. No. 3,350,216, in pertinent part, discloses silicone rubber which is made hydrophilic by dipping it into a solution of titanate. The titanium dioxide family of compounds have an undesirable property such as an extremely high index of refraction e.g. about 2.0 or about, and would not be suitable in the instant invention. The instant invention desires a low index of refraction e.g. 1.6 or below, such as found in the disclosed glasses for coating the instant silicone resinous materials. If a high index of refraction is used more scattering is obtained and a definite undesirable amount of reflection of light is evidenced on the surface.
Robert A. Erb, "Method for Protecting Wettable Surfaces on Contact Lenses by Chemical Formation of Inorganic Films," The Franklin Institute, Laboratories for Research & Development AFSAM Report 61-42, AD257290 NTIS, Springfield, Virginia 22151, in pertinent part, discloses a process of coating poly (methyl methacrylate) PMMA substrates with a thin film of titanium dioxide in order to make the surface hydrophilic for use as contact lenses. It is known that titanium dioxide and like compounds have an undesirable property such as extremely high indexes of refraction so that they are undesirable for use as coatings for contact lenses. High index of refraction gives more light scattering which interfers with the optics of the lens since there is a definite reflection of light on the surface. The glasses of the instant invention should have a relatively low index of refraction, e.g. 1.6 and below. It is known that the index of refraction of titanium dioxide is about 2.0 or above.
U.S. Pat. No. 3,228,741 discloses contact lenses made from silicone rubber particularly hydrocarbon substituted polysiloxane rubber. This silicone material contains fillers such as pure silica to control flexibility, pliability and resiliency of the lenses. The instant polymers require no fillers. Furthermore, '741 does not teach coating the silicone rubber.
U.S. Pat. No. 4,055,378 discloses, in pertinent part, a silicone elastomer contact lens containing a silicone dioxide filler for the elastomer. The filler is necessary in order to give added strength to the elastomer. The silicone elastomer is exposed to gas ions which impinge the outer layer and expose the silicon dioxide filler or transform the outer layer of silicone elastomer to silicone dioxide. It is disclosed that this process changes the hydrophobic surface to a hydrophilic surface. It is preferred in the instant invention to clean the surface of the silicone rubber by exposing the surface to oxygen plasma in a R.F. field or etch the surface with sputter etching but then the silicone rubber contact lens is coated with a continuous coating of glass.